1. Field of the Invention
This invention relates to novel processes for preparing intermediates [particularly 2-(arylhydrazino)succinonitrile compounds and 3-(arylhydrazono)propionitrile derivatives] useful in the preparation of pesticides.
2. Background of the Related Art
European Patent Publication Nos. 0295117 and 0234119 describe the preparation of pesticidally active phenylpyrazole compounds and of 5-amino-1-aryl-3-cyanopyrazole intermediate compounds used in their synthesis.
Various methods for preparing these compounds are known. The present invention seeks to provide improved or more economical methods for the preparation of pesticides and the intermediate compounds useful in preparing them.
German Patent Publication No. 3612940 discloses the preparation of 5-amino-1-arylpyrazole derivatives of general formula:

wherein Ar represents substituted phenyl or pyridyl, which can be used as intermediates in the preparation of compounds possessing herbicidal or pesticidal properties, by the reaction of arylhydrazine hydrochloride salts with formylacetonitrile sodium salt of the formula:NaOCH═CH—CN
to give hydrazone compounds of the general formula:Ar—NH—N═CH—CH2—CN
wherein Ar is as hereinbefore defined; which are then cyclized in the presence of a base.
However, it may be desirable to obtain the hydrazone compounds in a pure form useful for their further conversion into pesticides. Known procedures may result in the formation of hydrazones which are contaminated with the cyclized 5-amino-1-arylpyrazole product.
U.S. Pat. No. 4,824,960 describes the preparation of 5-amino-1-arylpyrazole derivatives of general formula:

wherein Ar represents substituted phenyl or pyridyl, which can be used as intermediates in the preparation of compounds possessing herbicidal or pesticidal properties, by the reaction of arylhydrazines of the formula:Ar—NH—NH2
wherein Ar is as hereinbefore defined, with acrylonitrile of the formula:NC—CH═CH2
in a first stage in the presence of a diluent and optionally a catalyst to give the 3-arylhydrazinopropionoitrile compounds of the formula:Ar—NH—NH—CH2—CH2—CN
wherein Ar is as hereinbefore defined, followed by oxidation and cyclization in a second process stage.
However, if it is desired to perform an oxidation of the above 3-arylhydrazinopropionitriles (without cyclization to the 5-amino-1-arylpyrazoles) in order to obtain 3-arylhydrazonopropionitriles, which may then be further processed to provide important 5-amino-1-aryl-3-cyanopyrazole compounds which are valuable intermediates in the preparation of pesticides, a different process must be employed.